Central Electronic Module on 2004 Volvo XC70

This has happened 1 time so far. Volvo can't find anything wrong with car. Diagnostics showed error codes for everything but yet once they unhooked car from machine it started right up and is running fine again. Air bag code and orange warning light were cleared but after 3 weeks they are back on again

I was driving on street 35mph. Car suddenly 'bucked', a 'thunk'sound came from it, then all power, electronics and engline died. Car was dead. I rolled into hard shoulder. No electrical power in car at all. After a few seconds i tried to start car, No power. Left car 5 mins, then car started, we went back on road, made it home turned car off waited 1 hour tried to start it and it would not start but had power back.

The Air bag code came on. and Orange Engine light came on.
Volvo cleared all the codes, said car ran fine. to stop the engine.

Volvo told me I may have to replace the CEM. (central Electronic module) if the engline dies again, but that is very expensive $1200.00.

Research on the web shows that many people with this make and model for 2004 are having the same issues

Asked by for the 2004 Volvo XC70
This is so infrequent that it will be very difficult for a shop to address. Has this happened since you first wrote this question a few weeks ago?
Yes two more times, last time just 3 days ago.
3 more answers , 1 more comment
Yeah,well the same thing just happened to me. And the volvo dealer also said to replace this module(CEM),so i was also looking for an answer.And this is very expensive. Great i wish I saw this last week before I purchased the car.
The car is equipped with a feature that if there is something that could potentially damage the transmission everything will shut off to protect the transmission from catastrophic failure. This happened to me after an expensive repair and someone forgot some bolts in there. So, maybe if the transmission fluid is old and hasn't been changed in a long time or there is some debris in there the same thing would happen. The driving would loosen the debris, stopping for a while would allow it to settle.
Electronically, there are other electronic modules, I know as I've had to replace them. So, if it's not the CEM it could be a different one.
I have a 2004 S80. It is in the shop for exactly the same reason.
so what did they repair?